Macroscopic Observation of Biotic-Abiotic Interactions in Biochar Layers Within a Sandy Soil in a Pot Trial with Wheat Triticum aestivum

Abstract

Biochar amendment of soils is an ancient technology which has attracted a lot of recent attention from soil scientists and environmentalists as a possible way to sequester carbon from the atmosphere in the soil, whilst increasing soil fertility. Wheat (Triticum aestivum) was grown for twelve weeks in pots were pine derived biochar was placed in two distinct layers within a sandy soil. The sandy and biochar layers were separated at harvesting to assess plant root growth, microbial biomass and degree of mycorrhizal root colonization. The biochar layers formed preferred zones for root development (P = 0.039) and microbial proliferation (P < 0.001) compared to the sandy layers. However, the degree of root mycorrhizal colonization decreased slightly in the two biochar layers and in the sandy layer between them, relative to the sandy layers above and below. The decrease in mycorrhizal colonization was possibly due to the enhancing effect that biochar has on water and nutrient retention. Furthermore, the physical and chemical characteristics of the biochar layers differed markedly from the sandy layers in terms of pH, cation exchange capacity, total C and available P. These factors have a strong influence on the micro-climate and nutrient status of each layer.